Port from KReportPageFormat to new KReportPageSize
API is simpler as uses QPageSize instead of custom defined sizes
Only ported a few of the page sizes in this version but more are easily added
Removed usage of QScreen to get DPI, and use KReportDpi everywhere, and
made KReportDpi return same for X and Y, as QPageSize uses a single resolution
to get px width/height.
Reviewed By: staniek
Differential Revision: https://phabricator.kde.org/D547